It is known in the art that nickel batteries that are repeatedly discharged to too high a voltage will develop what is referred to as "battery memory" or "voltage depression." This causes a loss of usable battery capacity until which time the battery is properly conditioned. To further accentuate the "memory" problem, battery fuel gauges found in wireless devices are often inaccurate. A typical "3 bar" radio fuel gauge display will show "0" bars when the battery still has approximately 10% of its capacity left. This 10% discharge point during transmit for a typical transceiver radio can be as high as 1.125V/cell. FIG. 1 is a graph 100 of prior art discharge curves for two nickel battery cells 102, 104. As shown in FIG. 1, discharging the nickel batteries down to 1.125V/cell causes the battery capacity of each cell to degrade to below 80% capacity within 20 cycles. This means that the typical user that recharges the battery as soon as the battery icon shows "0" bars will lose considerable battery capacity within 20 charge cycles due to the "memory" effect.
Many battery conditioners are available and are used for portable radio batteries to alleviate the "battery memory" problem and to enhance the battery cycle life performance. However, these conditioners are located external to the radio, typically residing in some form of table top charger or conditioner. The external conditioner typically requires significant board space and heat dissipation means. FIG. 2 is a block diagram of a prior art battery conditioning system described in U.S. Pat. No. 5,471,128 assigned to Motorola, Inc., which is herein incorporated by reference. Charging/Discharging system 200 includes a charge control circuit 224, a discharge control circuit 204, and a battery 222. The battery 222 is charged via the external charge circuit 224, and is discharged via the external discharge circuit 204.
The market demand for smaller wireless communication devices makes the use of large, heavy chargers and conditioners unattractive. There is a trend to incorporate much of the charging circuitry into the radio or battery. However, the conditioning circuitry has, thus far, been too cumbersome to incorporate into today's light weight products.
Accordingly, there is a need for an improved battery conditioning apparatus and technique that minimizes the use of external circuitry. Such a system would be beneficial of today's smaller communications devices.